1. Field of the Invention
This invention relates to a method for the enhanced recovery of oil from a reservoir. In one aspect, the invention relates to a method for caustic or alkaline waterflooding involving the addition of a lignosulfonate material to the injection fluid. In another aspect, the invention relates to the addition of a lignosulfonate material to seawater or other injection water to prevent the formation of precipitates upon mixing with a caustic material.
2. Discussion of the Art
Enhanced oil recovery (EOR) is a broad concept which encompasses many methods for increasing the recovery of oil remaining in a reservoir after the natural pressures are insufficient for economical production. Primary recovery from a reservoir often produces only 10 to 30 percent of the oil present in the formation. To recover at least a portion of the remaining oil, various supplemental methods are available. For example, a widely practiced secondary recovery technique involves the injection of a driving fluid such as water from one or more injection wells spaced at some distance from the producing well in order to force some of the oil towards the producing well. Tertiary recovery techniques following the waterflood could involve the addition of various amounts and combinations of surfactants, solvents, micellar compositions, and polymers. The reference to the terms secondary and tertiary is unimportant for the purposes of this application, and relates only to the sequence in which the supplemental or enhanced recovery methods are carried out.